Metal/plastic/metal composites, in particular, are known in the prior art. Under the tradename Litecor®, the applicant sells sandwich panels which consist of two sheet-steel cover layers having a material thickness between 0.2 to 0.3 mm, and a plastic core layer arranged between the sheet-steel cover layers and having a material thickness of at least 0.3 mm, these panels being outstandingly suitable as exterior and/or interior components of, in particular, a passenger automobile.
Additionally known from the prior art are components in particular for the paneling of, for example, commercial vehicles, especially of trailers, more particularly trunk constructions for refrigeration transport, composed of metal sandwich panels. In this case, for example, the outer surface used is a double-side hot-dip-galvanized coil coated steel panel, the inside surface used is a double-side hot-dip-galvanized steel panel coated with a food-resistant plastic, and a polyurethane foam core layer is used that is disposed between them (product information on “ISOPLUS II vario” from Rohr Nutzfahrzeuge). The steel panels used for the trunk construction have a material thickness of at least 0.6 mm. In order to ensure sufficient stability of the construction, and in view of the loads which occur during travel, which are high in particular, the specified thickness cannot be reduced further, at least not for this type of construction. In this field of application in particular, the potential for lightweight construction has not yet been exhausted. In other fields of application too, the possibility exists of making further weight savings in the context of the use of coil coated panels having material thicknesses of up to 3.0 mm, as in the case of garage doors, for example.
Also prior art is the form of strip coating referred to among experts as coil coating. As an example, information on the coating process can be picked up via the link http://de.wikipedia.org/wiki/Coil Coating. The coated substrates are generally steel strips, more particularly hot-dip-galvanized steel strips, and aluminum strips having material thicknesses of between 0.4 and 3.0 mm. Material thicknesses below 0.4 mm prove extremely difficult when implemented in coil coating lines, since coating over the full area, particularly at constant thickness, cannot be ensured on the relatively thin material.